[time-nuts] A different timenuts interest

Bob Bownes bownes at gmail.com
Wed Jul 21 22:40:48 EDT 2010


Silly me, I just realized you need to compensate for the change in
length with temperature.

This sounds like a great project!


On Wed, Jul 21, 2010 at 10:26 PM, Bob Bownes <bownes at gmail.com> wrote:
> There is at least one in DC, at the Smithsonian iirc.
>
> RPI, where I went to college, had one in the 3 story stairwell in the
> library. Don't know if it is still there.
>
> I remember one someplace in London too.
>
> Someone mentioned temperature compensation. What would you need to
> compensate for? Temp change in the wire wouldn't effect the rotation
> as far as I can tell. Swing length might be different based on temp of
> the wire I guess, but with a long pendulum, I think the magnet is
> going to way overcome that issue.
>
> The one @ RPI had issues due to air movement in the shaft, but that's
> a different problem.
>
> I suppose the right method is to use a GPS disciplined oscillator and
> the appropriate divider to drive the magnet under the floor. :) To cut
> down in draft induced drift and jitter, you'd have to put the whole
> thing in a vacuum though!
>
>
>
> On Wed, Jul 21, 2010 at 10:13 PM, Richard (Rick) Karlquist
> <richard at karlquist.com> wrote:
>>
>>
>> Hal Murray wrote:
>>
>>> Several years ago, I found a web site for a commercial place that made
>>> them for museums.  (I forget why I was looking for that sort of stuff.)  You
>>> might find interesting stuff/ideas via google but I didn't find a similar
>>> site with a bit of searching.
>>>
>>
>> The Museum of Science and Industry in Chicago had one when I lived
>> there in the 1960's.
>>
>> Rick N6RK
>>
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